Throttle servo choice

[Rctintin]

I was all set and happy with my choice of servos for the N7 until setting this heli up.

I have chosen Futaba BLS156HV cyclic servos which are .12s/60deg @ 7.4V direct lipo power.

In the build instructions, Matt said that a throttle servo would be best if it matched the cyclic speed or bettered it. Well, I have bought a Futaba S3072HV servo for the throttle, and its speed is slower at .15s/60@ 7.4v.

Now, .03s difference is almost nothing right? But I can see a huge difference in speed when I move the pitch stick on the Tx! The throttle lags behind a fair bit. Do any of you think this will matter?

To be honest, I'm not that impressed with this servo, but I suppose that comes from only using stupidly expensive servos in my heli's!! This has a plastic output gear, and it just sounds so noisy compared to the cyclic and tail servos!!

I'm in 2 minds with going with my heart and fitting a BLS451 for the throttle. Lightning fast and very smooth. Or, do I go with my head and leave this perfectly adequate servo in place?

[Jon Mills]

If you use a longer arm on your servo it will increase transit speed maybe try going out an extra hole just on the servo arm.  Also plastic gearing is absolutely fine on the throttle because it only pushes the throttle. With that being said, I have in the past used a 9254 rudder servo with great success on the throttle.  Ideally the throttle should be faster than the collective so the motor stays "ahead" of pitch demand.

[flyalan]

I used bls 255/256 on cyclic and a protek 250t on the throttle. I had considered a slower servo but I had the 250t so I used.  Less expensive than using another BLS255!

Cheers
Alan



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[cyprusflyer]

Are you sure it is your servo lagging? A Nitro engine cannot possibly respond as fast as a half decent servo can move the throttle arm. Just wonder if your governer controller is giving you that impression, ie mine has a slow ramp up to spool slowly etc (VBar). I am using a mini servo with an adapter plate (MKS HV9767 HV Mini Digital  Gear Cyclic Servo) and when plugged in directly it moves extremely fast but the VBar does its own thing, a lot of functions cannot be tested on the bench so a little leap of faith.

[Rctintin]

No engine running yet, this is just straight connection to V-Bar with no Gov setup yet. Its just plugged into the Th channel for now to centre the servo at 50/50 and set up the throttle linkage. Its a very noisy servo, and when you move full stick, its noticeable slower to get to its full throw compared to the cyclics.

I think I am going to go BLS451, I have those in most of my helis on cyclics, very fast and super smooth.

[flyalan]

CyprusFlyer has a good point. Just turn off the gov and see if that makes a difference. That being said I would heed matt's advice though.  I was also resistant but It does make sense and why cut corners. Yes you might save $50...
Don't be penny wise and pound foolish in regards to servos regardless of the application.
Cheers
Alan

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[Mike King]

Nice thing about throttle is you can find some pretty good speed specs out of servos that don't cost an arm and a leg.  Also don't need much in the way of torque as you are just rotating the throttle barrel.  Will be using an Align 620 on mine along with Futaba BLS272's on cyclic.

[Kevin Feil]

Protek 250t and bls255hv.

K

[Chris Sexton]

Bls 255hv on my throttle.

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[Rodney Kirstine]

I'm using the same RJX HV servo that I'm using as cyclic servos.

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[Darren Lee]

Rob, I am running a similar servo for my throttle, 3051HV I think.  Same as you, the first thing I noticed on the bench was how noisy it is and how obviously slow it is.  Many people say that throttle servo speed doesn't matter but I disagree.  My motor has a bad problem with overspeeding when taking load off suddenly.  I'm convinced the problem is my slow servo.  I'll be changing it out with something that matches or exceeds cyclic servo speed and report back with my findings.

[Jon Mills]

Nice thing about throttle is you can find some pretty good speed specs out of servos that don't cost an arm and a leg.  Also don't need much in the way of torque as you are just rotating the throttle barrel.  Will be using an Align 620 on mine along with Futaba BLS272's on cyclic.

+1 On this...

If you have an old rudder servo laying around or find one used, its a perfect application. 9254 futaba servo specs are lightning fast .05 and the amount of torque needed is nil. Just need a futaba inline regulator.

[Rctintin]

Well I have changed out the servo and installed my 'go to' favourite servo, the Futaba BLS451. Even though Futaba do not say its HV, Robbe their European arm lists it as suitable for HV, and I have them in my N5c, Goblin 700, TDR, etc etc all running HV, and never missed a beat. They are fast and super smooth.

[eobie]

Bls272hv on my throttle.

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[Chris Wall]

Does the Futaba servo allow you to mount the ball out and still have the throttle link run parallel to the body?  With the Torq servo (9180) the case sticks up too much and I have to mount the ball link on the inside which then barely clears the case of the servo on the OS throttle.  I just switched over to a YS120SRX and the linkage binds too much on the servo case.  So, looking for a nice low profile case servo to replace the Torq with...